JP5585942B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine provided with an EGR device that recirculates a part of exhaust gas of the internal combustion engine as EGR gas to an intake passage.

  Some internal combustion engines mounted on vehicles are equipped with an EGR device that recirculates a part of exhaust gas as EGR gas to an intake passage for the purpose of reducing fuel consumption or exhaust emission. Also, fuel cut control that stops fuel injection by stopping fuel injection when fuel cut conditions are satisfied during deceleration of the vehicle traveling, etc., and idle stop when the vehicle is decelerated or stopped just before the vehicle stops In some cases, idle stop control is performed to stop the fuel injection and ignition to stop the combustion of the internal combustion engine when the condition is satisfied.

  However, when an internal combustion engine equipped with an EGR device performs combustion stop control for stopping combustion of the internal combustion engine, such as fuel cut control or idle stop control, even if the EGR valve is closed, the EGR Since gas remains, a large amount of EGR gas may flow into the cylinder at the time of restart after execution of combustion stop control (after combustion stop), and the amount of EGR gas flowing into the cylinder at the time of restart is limited to the EGR limit. If (the upper limit of the amount of EGR gas that can be normally combusted) is exceeded, the combustion state may become unstable and the restartability may deteriorate.

  Therefore, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2009-191643), the timing at which the fuel cut condition is satisfied is predicted based on the road condition on which the vehicle travels, and the fuel cut condition is predicted to be satisfied. There is a technique in which processing for reducing the amount of EGR gas existing in the intake system of the internal combustion engine (for example, processing for controlling the opening degree of the EGR valve to the closed side) is performed at a time before a predetermined time.

JP 2009-191643 A

  However, in the technique of the above-mentioned Patent Document 1, a process for reducing the amount of EGR gas existing in the intake system is performed, but since there is no function for determining the amount of EGR gas actually flowing into the cylinder, combustion is performed. There is a possibility that the amount of EGR gas flowing into the cylinder at the time of restart after execution of stop control is not sufficiently reduced. In such a case, the combustion state becomes unstable and the restartability may be deteriorated. There is.

  Accordingly, the problem to be solved by the present invention is to provide a control device for an internal combustion engine that can prevent the combustion state from becoming unstable during restart after execution of combustion stop control and improve restartability. There is to do.

In order to solve the above-mentioned problems, an invention according to claim 1 is directed to an EGR pipe that recirculates a part of exhaust gas of an internal combustion engine as an EGR gas to an intake passage upstream of a throttle valve, and an EGR gas that flows in the EGR pipe An internal combustion engine comprising a low pressure loop type EGR device having an EGR valve for adjusting a flow rate, and combustion stop control means for executing combustion stop control for stopping combustion of the internal combustion engine when a predetermined combustion stop request is generated In the control device, in-cylinder inflow EGR gas amount determination for calculating the amount of EGR gas flowing into the cylinder of the internal combustion engine or information related thereto (hereinafter collectively referred to as “in-cylinder inflow EGR gas amount information”). retardant executing means and the combustion stop delay control to delay the execution of the combustion stop control based on the cylinder-inflow EGR gas amount information calculated by the cylinder inflow EGR gas amount determination means And a stop delay control means, the cylinder inflow EGR gas amount determination means, by using the EGR valve model EGR gas flowing through the EGR inside pipe simulating a behavior that passes through the EGR valve, passes through the EGR valve The EGR gas flow rate (hereinafter referred to as “EGR valve passage gas flow rate”) is calculated, and the EGR gas delay that simulates the behavior of the EGR gas that has passed through the EGR valve and flows into the cylinder through the throttle valve Using the model, the in-cylinder inflow EGR gas amount information is calculated based on the EGR valve passing gas flow rate calculated by the EGR valve model.

In this configuration, the in- cylinder inflow EGR gas amount information (the amount of EGR gas flowing into the cylinder) can be determined by calculating the in-cylinder inflow EGR gas amount information using the EGR valve model and the EGR gas delay model. By executing the combustion stop delay control that delays the execution of the combustion stop control based on the calculated in-cylinder inflow EGR gas amount information, the EGR remaining in the intake passage even when a combustion stop request is generated The combustion stop control is delayed until the in-cylinder inflow EGR gas amount is sufficiently reduced after the gas is scavenged, and after the in-cylinder inflow EGR gas amount is sufficiently reduced, the combustion stop control is executed to execute the internal combustion engine. Can be stopped. This prevents the amount of in-cylinder inflow EGR gas from exceeding the EGR limit (the upper limit of the amount of EGR gas that can be normally burned) at the time of restart after execution of combustion stop control (after combustion stop). Instability can be prevented and restartability can be improved.

  In this case, as in claim 2, it is determined based on the in-cylinder inflow EGR gas amount information whether normal combustion is possible at restart after execution of combustion stop control, and normal combustion is not possible at the restart. It is preferable to execute the combustion stop delay control when it is determined that there is no possibility (the combustion state may become unstable). If it does in this way, it can prevent reliably that a combustion state becomes unstable at the time of restart after execution of combustion stop control.

  Furthermore, as in claim 3, when it is determined that normal combustion is possible at the time of restart after execution of the combustion stop control based on the in-cylinder inflow EGR gas amount information during execution of the combustion stop delay control, the combustion stop delay It is better to release the control. In this way, it is possible to prevent the combustion stop delay control from becoming longer than necessary (that is, delaying the execution of the combustion stop control more than necessary).

  Further, as in claim 4, the combustion stop delay control is prohibited when the driver performs a stop operation of the internal combustion engine and / or when an airbag signal for operating the airbag is output. May be. In this way, when the driver performs a stop operation of the internal combustion engine (for example, turns off the ignition switch), or when an airbag signal is output due to a vehicle collision, the inflow EGR gas amount in the cylinder Regardless of the information, the combustion stop control can be executed promptly to quickly stop the combustion of the internal combustion engine.

FIG. 1 is a diagram showing a schematic configuration of an engine control system with a supercharger in one embodiment of the present invention. FIG. 2 is a flowchart showing the flow of processing of the combustion stop delay control routine. FIG. 3 is a block diagram illustrating a method of calculating the in-cylinder inflow EGR gas flow rate. FIG. 4 is a diagram for explaining the EGR valve model. FIG. 5 is a block diagram illustrating the EGR gas delay model. FIG. 6 is a diagram for explaining an intake pipe advection delay model. FIG. 7 is a time chart showing an execution example of the combustion stop delay control. FIG. 8 is a time chart showing an execution example of conventional combustion stop control.

Hereinafter, an embodiment in which the embodiment for carrying out the present invention is applied to an internal combustion engine with a supercharger will be described.
First, based on FIG. 1, the structure of the engine control system with a supercharger is demonstrated roughly.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 (intake passage) of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the flow rate of intake air (fresh air) is provided downstream of the air cleaner 13. Is provided. On the other hand, the exhaust pipe 15 (exhaust passage) of the engine 11 is provided with a catalyst 16 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas.

  The engine 11 is equipped with an exhaust turbine driven supercharger 17 that supercharges intake air. In the supercharger 17, an exhaust turbine 18 is disposed on the upstream side of the catalyst 16 in the exhaust pipe 15, and a compressor 19 is disposed on the downstream side of the air flow meter 14 in the intake pipe 12. The supercharger 17 is connected so that the exhaust turbine 18 and the compressor 19 rotate integrally, and the exhaust turbine 18 is rotationally driven by the kinetic energy of the exhaust gas, so that the compressor 19 is rotationally driven to suck the intake air. It is supposed to supercharge.

  A throttle valve 21 whose opening is adjusted by a motor 20 and a throttle opening sensor 22 that detects the opening (throttle opening) of the throttle valve 21 are provided on the downstream side of the compressor 19 in the intake pipe 12. It has been.

  Further, an intercooler for cooling the intake air is provided integrally with the surge tank 23 (intake passage) on the downstream side of the throttle valve 21. An intercooler may be arranged upstream of the surge tank 23 and the throttle valve 21. The surge tank 23 is provided with an intake manifold 24 (intake passage) for introducing air into each cylinder of the engine 11, and a fuel injection valve (not shown) for performing in-cylinder injection or intake port injection is attached to each cylinder. It has been. An ignition plug (not shown) is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in each cylinder is ignited by spark discharge of each ignition plug.

  An exhaust manifold 25 is connected to the exhaust port of each cylinder of the engine 11, and a downstream collecting portion of the exhaust manifold 25 of each cylinder is connected to an exhaust pipe 15 upstream of the exhaust turbine 18. An exhaust bypass passage 26 that bypasses the upstream side and the downstream side of the exhaust turbine 18 is provided, and a waste gate valve 27 that opens and closes the exhaust bypass passage 26 is provided in the exhaust bypass passage 26.

  The engine 11 is equipped with an LPL type (low pressure loop type) EGR device 28 that recirculates a part of the exhaust gas from the exhaust pipe 15 to the intake pipe 12 as EGR gas. The EGR device 28 includes an EGR pipe 29 (EGR passage) between the downstream side of the catalyst 16 in the exhaust pipe 15 and the upstream side of the compressor 19 in the intake pipe 12 (intake passage on the upstream side of the throttle valve 21). The EGR pipe 29 is provided with an EGR cooler 30 for cooling the EGR gas and an EGR valve 31 for adjusting the EGR gas flow rate. The opening degree of the EGR valve 31 is adjusted by an actuator (not shown) such as a motor, and the EGR valve 31 is opened to open a compressor in the intake pipe 12 from the downstream side of the catalyst 16 in the exhaust pipe 15. The EGR gas is recirculated to the upstream side 19 (the intake passage on the upstream side of the throttle valve 21).

  The engine 11 also includes an intake side variable valve timing mechanism 32 that changes the valve timing (opening / closing timing) of an intake valve (not shown), and an exhaust side variable valve that changes the valve timing of an exhaust valve (not shown). A timing mechanism 33 is provided. In addition, the engine 11 is provided with a coolant temperature sensor 34 that detects the coolant temperature, a crank angle sensor 35 that outputs a pulse signal each time a crankshaft (not shown) rotates a predetermined crank angle, and the like. Based on the output signal 35, the crank angle and the engine speed are detected.

  Outputs of these various sensors are input to an electronic control unit (hereinafter referred to as “ECU”) 36. The ECU 36 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount and the ignition timing according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

  At that time, the ECU 36 calculates a target EGR rate according to the engine operating state (for example, engine load and engine speed), and controls the opening degree of the EGR valve 31 so as to realize the target EGR rate.

  Further, the ECU 36 executes fuel cut control for stopping the fuel injection and stopping the combustion of the engine 11 when a fuel cut condition is satisfied and a combustion stop request is generated at the time of deceleration while the vehicle is running, Idle stop control is executed to stop the fuel injection and / or ignition to stop the combustion of the engine 11 when an idle stop condition is satisfied and a combustion stop request is generated at the time of deceleration immediately before stopping or at the time of stopping. These functions serve as combustion stop control means in the claims.

  However, when the engine 11 equipped with the EGR device 28 executes the combustion stop control for stopping the combustion of the engine 11 such as the fuel cut control or the idle stop control, the intake pipe 12 does not stop even if the EGR valve 31 is closed. Since EGR gas remains in the cylinder, a large amount of EGR gas may flow into the cylinder during restart after the combustion stop control is performed (after combustion stop), and the amount of EGR gas that flows into the cylinder during restart Exceeds the EGR limit (the upper limit of the amount of EGR gas that can be normally burned), the combustion state may become unstable, and the restartability may deteriorate.

  As a countermeasure against this, in this embodiment, the ECU 36 executes a combustion stop delay control routine shown in FIG. 2 to be described later, so that an estimation method (see FIGS. 3 to 6), which will be described later. Whether or not normal combustion is possible at restart after execution of combustion stop control (after combustion stop) by comparing the in-cylinder inflow EGR gas amount with a normal combustion determination threshold value Determine. As a result, if it is determined that normal combustion is not possible at the time of restart after execution of combustion stop control (combustion state may become unstable), combustion stop delay control that delays execution of combustion stop control Execute. After that, when it is determined that normal combustion is possible at the time of restart after executing the combustion stop control based on the in-cylinder inflow EGR gas amount during the execution of the combustion stop delay control, the combustion stop delay control is canceled and the combustion is stopped. Execute control.

The processing contents of the combustion stop delay control routine of FIG. 2 executed by the ECU 36 in this embodiment will be described below.
The combustion stop delay control routine shown in FIG. 2 is repeatedly executed at a predetermined period during the power-on period of the ECU 36, and serves as a combustion stop delay control means in the claims. When this routine is started, first, in step 101, an in-cylinder inflow EGR gas amount estimation routine (not shown) is executed, whereby the in-cylinder inflow EGR gas amount is determined by an estimation method (see FIGS. 3 to 6) described later. presume. The processing in step 101 serves as a cylinder inflow EGR gas amount determination means in the claims.

  Thereafter, the process proceeds to step 102, and a normal combustion determination threshold value corresponding to the engine operating state (for example, engine load and engine speed) and the coolant temperature is calculated by a map or a mathematical expression. The normal combustion determination threshold value is set to an upper limit value of the in-cylinder inflow EGR gas amount that can be normally burned at the time of restart after execution of combustion stop control (after combustion stop) or a value that is smaller by a predetermined amount.

  For example, the normal combustion determination threshold value map or mathematical formula is such that the normal combustion determination threshold value decreases as the engine load (for example, intake air amount or intake pipe pressure) decreases, and the normal combustion determination threshold value decreases as the engine speed decreases. Furthermore, the normal combustion determination threshold is set to be smaller as the cooling water temperature is lower. The normal combustion determination threshold value map or mathematical expression is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 36.

Thereafter, the routine proceeds to step 103, where the in-cylinder inflow EGR gas amount is compared with a normal combustion determination threshold value to determine whether normal combustion is possible at the time of restart after execution of the combustion stop control.
If it is determined in step 103 that the in-cylinder inflow EGR gas amount is larger than the normal combustion determination threshold value, normal combustion is not possible at the time of restart after execution of the combustion stop control (the combustion state becomes unstable). The process proceeds to step 104, and whether or not the driver has performed an engine stop operation (for example, turning off the ignition switch) or whether an airbag signal for operating the airbag has been output. Determine whether.

  If it is determined in this step 104 that the engine stop operation has been performed by the driver, or if it is determined that the airbag signal has been output, the routine proceeds to step 106 where combustion stop control is permitted and combustion stop delay is performed. Prohibit control. As a result, when the driver performs an engine stop operation and a combustion stop request is generated, or when a vehicle crashes and an airbag signal is output and a combustion stop request is generated, the combustion stop control is promptly performed. This is executed to quickly stop the combustion of the engine 11.

  On the other hand, if it is determined in step 104 that the engine stop operation has not been performed by the driver and it is determined that the airbag signal has not been output, the process proceeds to step 105 and combustion stop control is prohibited. To do. Thus, even if the fuel cut condition or the idle stop condition is satisfied and the combustion stop request is generated, the combustion stop delay control for delaying the execution of the combustion stop control is executed, and the combustion of the engine 11 (fuel injection and ignition) is performed. ).

  Thereafter, during the execution of the combustion stop delay control, if it is determined in step 103 that the in-cylinder inflow EGR gas amount is equal to or less than the normal combustion determination threshold, normal combustion is possible at the restart after the execution of the combustion stop control. Is determined to proceed to step 106, and combustion stop control is permitted. As a result, the combustion delay control is canceled, and the combustion stop control for stopping the fuel injection and ignition to stop the combustion of the engine 11 is executed.

Next, a method for estimating the in-cylinder inflow EGR gas amount will be described with reference to FIGS.
In the case of a system that employs an LPL type EGR device 28 that recirculates EGR gas to the upstream side of the compressor 19 (the intake passage on the upstream side of the throttle valve 21) of the intake pipe 12 as in this embodiment, The ECU 36 calculates (estimates) the in-cylinder inflow EGR gas flow rate as follows.

  As shown in FIG. 3, the in-cylinder inflow total gas flow rate calculation unit 37 first uses a throttle model 39 that simulates the behavior of the gas flowing through the intake pipe 12 passing through the throttle valve 21, and uses the throttle-through total gas flow rate. (Total gas flow rate passing through the throttle valve 21) is calculated. As the throttle model 39, for example, a throttle model described in Patent Document 1 (Japanese Patent Laid-Open No. 2008-101626) may be used.

  Thereafter, using the intake manifold model 40 simulating the behavior that the gas that has passed through the throttle valve 21 is filled into the intake passage (surge tank 23, intake manifold 24, etc.) on the downstream side of the throttle valve 21, the total gas passing through the throttle is used. The intake manifold pressure (pressure in the intake passage on the downstream side of the throttle valve 21) is calculated based on the flow rate and the previous value of the in-cylinder inflow total gas flow rate. As the intake manifold model 40, for example, an intake pipe model described in Patent Document 1 (Japanese Patent Laid-Open No. 2008-101626) may be used.

  Thereafter, the in-cylinder inflow total gas flow rate (= cylinder) based on the intake manifold pressure using the intake valve model 41 simulating the behavior that the gas filled in the intake passage on the downstream side of the throttle valve 21 is sucked into the cylinder. The inflow fresh air flow rate + the inflow in-cylinder EGR gas flow rate) is calculated. As the intake valve model 41, for example, an intake valve model described in Patent Document 1 (Japanese Patent Laid-Open No. 2008-101626) may be used.

  On the other hand, the in-cylinder inflow EGR gas flow rate calculation unit 38 first uses an EGR valve model 42 simulating the behavior of EGR gas flowing in the EGR pipe 29 passing through the EGR valve 31, and uses an EGR valve passing gas flow rate (EGR valve). EGR gas flow rate passing through 31 is calculated.

  As shown in FIG. 4, the EGR valve model 42 is constructed by a map that defines the relationship between the opening degree of the EGR valve 31, the throttle passage total gas flow rate, and the EGR valve passage gas flow rate, and this EGR valve passage gas flow rate map. Is used to calculate the EGR valve passage gas flow rate according to the opening degree of the EGR valve 31 and the throttle passage total gas flow rate. The map of the EGR valve passage gas flow rate is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 36.

Alternatively, the EGR valve model 42 is constructed by a physical formula that defines the relationship between the opening degree of the EGR valve 31, the pressure Pin on the upstream side of the EGR valve 31 and the pressure Pout on the downstream side, and the EGR valve passage gas flow rate Megr. Anyway.
Specifically, the EGR valve model 42 is approximated by the following throttle equation (orifice equation).

  Here, C is a flow coefficient, and A is an opening cross-sectional area of the EGR pipe 29 that changes in accordance with the opening degree of the EGR valve 31. R is a gas constant, Tegr is the temperature of the EGR gas upstream of the EGR valve 31, and Φ (Pout / Pin) is a function with (Pout / Pin) as a variable.

  In this case, the EGR valve 31 is based on the opening degree of the EGR valve 31, the pressure Pin on the upstream side of the EGR valve 31, the pressure Pout on the downstream side, and the temperature of the EGR gas, using the above-described throttle equation (orifice equation). The passing gas flow rate Megr is calculated.

  Thereafter, the EGR valve passage gas flow rate is measured using an EGR gas delay model 43 (see FIG. 3) that simulates the behavior of the EGR gas that has passed through the EGR valve 31 until it passes through the throttle valve 21 and flows into the cylinder. A cylinder inflow EGR gas flow rate is calculated based on the calculated value.

  As shown in FIG. 5, the EGR gas delay model 43 has a behavior in which the EGR gas that has passed through the EGR valve 31 flows into the intake passage on the upstream side of the throttle valve 21 (the upstream side of the compressor 19 in the intake pipe 12). Passing through the throttle valve 21, the simulated new air lag model 44, the intake pipe advection delay model 45 simulating the behavior of the EGR gas flowing into the intake passage upstream of the throttle valve 21 through the throttle valve 21, The intake manifold filling delay model 46 simulating the behavior of the EGR gas filled in the intake passage (surge tank 23, intake manifold 24, etc.) downstream of the throttle valve 21 and the intake passage downstream of the throttle valve 21 filled. Intake port advection delay simulating the behavior of EGR gas passing through the intake port and flowing into the cylinder And a Dell 47 Metropolitan.

  Thereby, the delay when the EGR gas flows into the intake passage on the upstream side of the throttle valve 21 and the advancing delay until the EGR gas that flows into the intake passage on the upstream side of the throttle valve 21 passes through the throttle valve 21; The filling delay when the EGR gas that has passed through the throttle valve 21 is filled in the intake passage on the downstream side of the throttle valve 21, and the EGR gas that has been filled in the intake passage on the downstream side of the throttle valve 21 passes through the intake port. The advection delay until it flows into the cylinder can be reflected in the calculation of the in-cylinder inflow EGR gas flow rate, and the estimation accuracy of the in-cylinder inflow EGR gas flow rate can be improved.

  When calculating the in-cylinder inflow EGR gas flow rate, first, the EGR flow delay model 44 is used, and EGR flows into the intake passage on the upstream side of the throttle valve 21 based on the EGR valve passage gas flow rate Megr (a). The gas flow rate Megr (b) is calculated.

The new convection delay model is approximated by the following equation (1).
Megr (b) = {K1 / (τ1 + 1)} × Megr (a) (1)
The coefficient K1 and the time constant τ1 in the above equation (1) are determined by the pipe diameter and length of the EGR pipe 29 (portion from the EGR valve 31 to the junction with the intake pipe 12), the pipe diameter of the intake pipe 12, etc. Value, which is calculated in advance based on test data, design data, and the like.

  Thereafter, using the intake pipe advection delay model 45, the EGR passing through the throttle valve 21 based on the EGR gas flow rate Megr (b) flowing into the intake passage upstream of the throttle valve 21 and the throttle passage total gas flow rate Mth. The gas flow rate Megr (c) is calculated.

  As shown in FIG. 6, the intake pipe advection delay model 45 discretizes the behavior of the continuous time system until the EGR gas flowing into the intake passage on the upstream side of the throttle valve 21 passes through the throttle valve 21 at an arbitrary time. The queue is constructed by a matrix (for example, 32 matrices discretized every 16 ms of sample time) and holds data in a first-in first-out list structure. In general, the transfer speed of the EGR gas in the intake pipe 12 is sufficiently slower than the calculation processing speed of the ECU 36, and therefore the intake pipe advection delay model 45 can be constructed by a matrix discretized at an arbitrary time. The various coefficients used in the intake pipe advection delay model 45 are values determined by the pipe diameter and length of the intake pipe 12 (the portion from the junction with the EGR pipe 29 to the throttle valve 21), respectively, Or based on design data or the like.

  Thereafter, as shown in FIG. 5, an intake passage on the downstream side of the throttle valve 21 based on the EGR gas flow rate Megr (c) passing through the throttle valve 21 using the intake manifold filling delay model 46 (the surge tank 23 and the intake air EGR gas flow rate Megr (d) filled in the manifold 24 or the like is calculated.

The intake manifold filling delay model 46 is approximated by the following equation (2).
Megr (d) = {K 2 / (τ 2 +1)} × Megr (c) (2)

  The coefficient K2 and the intake manifold filling delay time constant τ2 in the above equation (2) are the intake passages on the downstream side of the throttle valve 21 (the portion of the intake pipe 12 downstream of the throttle valve 21, the surge tank 23, the intake manifold 24). Etc.) is determined based on test data, design data, and the like in advance. When the intake manifold filling delay time constant is used in the intake manifold model 40, the intake manifold filling delay time constant used in the intake manifold model 40 may be used in the intake manifold filling delay model 46.

  Thereafter, using the intake port advection delay model 47, the cylinder inflow is based on the EGR gas flow rate Megr (d) filled in the intake passage downstream of the throttle valve 21 and the previous value of the in-cylinder inflow total gas flow rate. The EGR gas flow rate Megr (e) is calculated.

  The intake port advection delay model 47 is a matrix in which the behavior of a continuous time system from when the EGR gas filled in the intake passage on the downstream side of the throttle valve 21 passes through the intake port and flows into the cylinder is discretized at an arbitrary time. And a queue that holds data in a first-in first-out list structure. Various coefficients used in the intake port advection delay model 47 are values determined by the pipe diameter and length of the intake port, respectively, and are calculated based on test data, design data, and the like in advance.

  As shown in FIG. 8, in the conventional combustion stop control, for example, at the time t1 when the idle stop condition is satisfied and the combustion stop request is generated when the accelerator opening is fully closed, the combustion stop flag is turned on. Combustion stop control for stopping fuel injection and ignition to stop the combustion of the engine 11 is executed. In this case, since the EGR gas remains in the intake pipe 12 even when the EGR valve 31 is closed, at the time t2 when the restart condition is satisfied and restarted after execution of the combustion stop control (after the combustion stop). A large amount of EGR gas may flow into the cylinder, and if the amount of EGR gas flowing into the cylinder during restart exceeds the EGR limit (the upper limit of the amount of EGR gas that can be normally burned), the combustion state is unstable. The misfire may occur and the restartability may deteriorate.

  On the other hand, as shown in FIG. 7, in this embodiment, for example, the in-cylinder inflow EGR gas amount is normal at time t1 when the idle stop condition is satisfied and the combustion stop request is generated when the accelerator opening is fully closed. If it is greater than the combustion determination threshold, it is determined that normal combustion is not possible (combustion state may become unstable) at the time of restart after execution of combustion stop control (after combustion stop), and combustion is stopped. The combustion stop control is prohibited by keeping the flag OFF. Thereby, even if the combustion stop request | requirement has generate | occur | produced, the combustion stop delay control which delays execution of combustion stop control is performed, and combustion (fuel injection and ignition) of the engine 11 is continued.

  Thereafter, at the time t2 when the in-cylinder inflow EGR gas amount becomes equal to or less than the normal combustion determination threshold value during the execution of the combustion stop delay control, it is determined that normal combustion is possible at the restart after the execution of the combustion stop control. The combustion stop flag is turned on to allow combustion stop control. As a result, the combustion delay control is canceled, and the combustion stop control for stopping the fuel injection and ignition to stop the combustion of the engine 11 is executed.

  In the present embodiment described above, since the in-cylinder inflow EGR gas amount (the EGR gas amount flowing into the cylinder) is estimated, the in-cylinder inflow EGR gas amount can be determined, and the estimated cylinder Since the combustion stop delay control for delaying the execution of the combustion stop control is executed based on the inflow EGR gas amount, the EGR gas remaining in the intake pipe 12 is scavenged even when the combustion stop request is generated. The execution of the combustion stop control is delayed until the in-cylinder inflow EGR gas amount is sufficiently reduced, and the combustion stop control is executed after the in-cylinder inflow EGR gas amount is sufficiently reduced to stop the combustion of the engine 11. You can This prevents the amount of in-cylinder inflow EGR gas from exceeding the EGR limit (the upper limit of the amount of EGR gas that can be normally burned) at the time of restart after execution of combustion stop control (after combustion stop). Instability can be prevented and restartability can be improved.

  Further, in this embodiment, the in-cylinder inflow EGR gas amount is compared with a normal combustion determination threshold value to determine whether normal combustion is possible at restart after execution of combustion stop control, and normal combustion at restart The combustion stop delay control is executed when it is determined that this is not possible (combustion state may be unstable), so the combustion state becomes unstable when restarting after the combustion stop control is executed. Can be reliably prevented.

  Further, in this embodiment, when it is determined that the in-cylinder inflow EGR gas amount becomes equal to or less than the normal combustion determination threshold value during the combustion stop delay control, and normal combustion is possible at the restart after the combustion stop control is executed. Furthermore, since the combustion stop delay control is canceled and the combustion stop control is executed, it is possible to prevent the combustion stop delay control from becoming longer than necessary (that is, delaying the execution of the combustion stop control more than necessary). be able to.

  Further, in this embodiment, the combustion stop delay control is prohibited when an engine stop operation (for example, turning off the ignition switch) is performed by the driver or when an airbag signal for operating the airbag is output. As a result, when the driver performs an engine stop operation or when a vehicle collides and an airbag signal is output, the combustion stop control is promptly performed regardless of the in-cylinder inflow EGR gas amount. By executing this, the combustion of the engine 11 can be stopped quickly.

  In the above embodiment, the present invention is applied to a system that executes combustion stop control when a fuel cut condition or an idle stop condition is satisfied and a combustion stop request is generated. However, the present invention is not limited to this. The present invention is applied to a system that executes combustion stop control in a hybrid vehicle that uses both a motor and a motor as a power source, when a motor travel condition that travels only with the power of the motor is established and a combustion stop request is generated. Anyway.

  Further, the present invention is not limited to an engine equipped with an exhaust turbine-driven supercharger (so-called turbocharger), but is equipped with a machine-driven supercharger (so-called supercharger) or an electric supercharger. It may be applied to the engine.

  In addition, the present invention is not limited to an engine with a supercharger, and may be applied to a naturally aspirated engine (NA engine) not equipped with a supercharger.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe (intake passage), 15 ... Exhaust pipe, 17 ... Supercharger, 21 ... Throttle valve, 23 ... Surge tank, 24 ... Intake manifold, 28 ... EGR device, 29 ... EGR piping (EGR passage), 31... EGR valve, 36... ECU (combustion stop control means, cylinder inflow EGR gas amount determination means, combustion stop delay control means)

Claims (4)

A low-pressure loop EGR device having an EGR pipe that recirculates a part of the exhaust gas of the internal combustion engine as EGR gas to an intake passage upstream of the throttle valve and an EGR valve that adjusts the flow rate of the EGR gas flowing in the EGR pipe ; In a control device for an internal combustion engine comprising combustion stop control means for executing combustion stop control for stopping combustion of the internal combustion engine when a predetermined combustion stop request is generated,
In-cylinder inflow EGR gas amount determination means for calculating the amount of EGR gas flowing into the cylinder of the internal combustion engine or information related thereto (hereinafter collectively referred to as “in-cylinder inflow EGR gas amount information”); Combustion stop delay control means for executing combustion stop delay control for delaying execution of the combustion stop control based on in-cylinder inflow EGR gas amount information calculated by the in-cylinder inflow EGR gas amount determination means ,
The in-cylinder inflow EGR gas amount determining means uses an EGR valve model that simulates the behavior of EGR gas flowing through the EGR pipe and passing through the EGR valve, and uses the EGR gas flow rate (hereinafter referred to as “EGR”) that passes through the EGR valve. The EGR valve is calculated using an EGR gas delay model that simulates the behavior of the EGR gas that has passed through the EGR valve and flows into the cylinder through the throttle valve. An in-cylinder inflow EGR gas amount information is calculated based on the EGR valve passage gas flow rate calculated by a model .   The combustion stop delay control means determines whether normal combustion is possible at restart after execution of the combustion stop control based on the in-cylinder inflow EGR gas amount information, and normal combustion is not possible at the restart. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the combustion stop delay control is executed when it is determined that there is not.   When the combustion stop delay control means determines that normal combustion is possible at restart after execution of the combustion stop control based on the in-cylinder inflow EGR gas amount information during execution of the combustion stop delay control, The control device for an internal combustion engine according to claim 2, wherein the combustion stop delay control is canceled.   The combustion stop delay control means is a means for prohibiting the combustion stop delay control when a stop operation of the internal combustion engine is performed by a driver and / or when an airbag signal for operating the airbag is output. The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising:

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